Did this solve your problem?

If you've set your phone to use a specific network mode, it can't get a network connection if the selected network mode is out of range.

Turn on automatic network mode selection.

Step of :

Turn on automatic network mode selection.

of

1. Find "Network mode"

Slide your finger downwards starting from the top of the screen.

Tap the settings icon.

Tap Connections.

Tap Mobile networks.

Tap Network mode.

2. Select network mode

Tap the required network mode.

There may be different network modes available depending on where you are. If you set your phone to the fastest network mode, it will always find the network with the highest data speed and best signal.